1. Field of the Invention
The present invention relates to a field emission display, and, more particularly, to a field emission display having carbon nanotube emitters.
2. Description of the Related Art
The field emission display (FED) uses cold cathodes as the source for emitting electrons to realize images. The overall quality of the FED depends on the characteristics of emitters, which form an electron-emitting layer. The first FEDs utilized emitters made mainly of molybdenum (Mo), that is, the emitters were formed of what are referred to as Spindt-type metal tips. As an example of such conventional technology, a display system that has field emission cathodes is disclosed in U.S. Pat. No. 3,789,471.
However, during the manufacture of the FED having metal tip emitters, a semiconductor manufacturing process is used, such as photolithography and etching processes to form holes into which emitters are provided and the process of depositing molybdenum to form metal tips. Not only is production complicated and a high technology is needed, but expensive equipment is also required, thereby increasing overall unit costs. These factors make the mass production of such FEDs problematic.
Accordingly, a great deal of research and development is being performed by those in the FED industry to form emitters that enable electron emission at low voltages (10˜50V) and simple manufacture of the emitter structure. It is known that carbon-based materials, for example, graphite, diamond, DLC (diamond like carbon), C60 (Fullerene), and carbon nanotubes are suitable for use in the manufacture of such flat emitters. In particular, it is believed that carbon nanotubes, with their ability to realize electron emission at relatively low driving voltages of approximately 10˜50V, is the ideal emitter configuration for FEDs.
U.S. Pat. Nos. 6,062,931 and 6,097,138 disclose cold cathode field emission displays that are related to this area of FEDs, using carbon nanotube technology. The FEDs disclosed in these patents employ a triode structure having cathode electrodes, an anode electrode, and gate electrodes. During the manufacture of these FEDs, the cathode electrodes are first formed on a substrate. Then, after providing emitters on the cathode electrodes, the gate electrodes are formed on the emitters. That is, the conventional FEDs have a structure in which the gate electrodes are provided between the cathode electrodes and the anode electrode, and electrons emitted from the emitters are induced toward a phosphor layer(s).
To improve the characteristics of the FED, the above triode structure is used and the emitters are formed using a carbon-based material (i.e., carbon nanotubes). However, it is difficult to precisely form the emitters in holes formed in an insulation layer, which is provided under the gate electrodes. This is a result of the difficulties involved in forming the emitters with a printing process that uses paste. In particular, it is very difficult to provide the paste in the minute holes for formation of the emitters.
Further, with respect to the FED having the conventional triode structure, when the electrons emitted from the emitters form electron beams and travel in this state toward their intended phosphors, there are instances when an excessive diverging force of the electron beams is given by the gate electrodes when passing a region of the gate electrodes to which a positive voltage is applied. In such a case, the electron beam emitted from an emitter illuminates a phosphor adjacent to the intended phosphor as a result of the undesirable re-direction of the electron beams. This reduces color purity and overall picture quality of the FED.